Traverse start control



C. c. w. WILLIAMS ETAL TRAVERSE START CONTROL Filed Sept. 14, 1954 2 Sheets-Sheet 1 Mangia;

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zw !Illllliillllllllllllll @a 35403 e, vp gggiai TN ATTORNEY Oct. 28, 1958 c. c. w. WILLIAMS ET AL 2,857,885

TRAVERSE START CONTROL f Filed Sept. 14, 1954 2A Shees-Sheet 2' INVENTO RS C. C. WALKER WILL/A MS BY HAR L0 .BALS/GER )UQQLJ ATTORNEY United States Patent() 2,857,886 TRAVERSE START CONTROL Application September 14, 1.954, Serial No- 455,820 7 Claims. (Cl, 121- 45) This invention relates to hydraulic control mechansms .far machin@ toQl carriages and thelike. j One problem heretofore considered negligible has become important because of new procedures and more rigid requirements in grinding. This problem has to do with the' starting characteristics of hydraulically driven members on machine tools such as work carriages in which the carriage is quite frequently inclined to start with a lurch rather than to accelerate smoothly to the required speed. This .problem exists only 'after the carriage has been at rest for some time and not during reversal of the carriage once the carriage has been put in motion.

This invention proposes to solve the problem by providing substantially equal pressure on both sides of the hydraulic motor and then gradually reducing the pressure on one side to exhaust pressure.

It` is an object of this invention to provide means` Vfor effecting a smooth start =for a hydraulically actuated slide.

A Q further object is to provide means for resisting the movement of the carriage and thereafter graduallly reducing the magnitude of resistance.

A further object is to provide a valve ttor blocling a discharge `ofexhaust `iluid from a hydraulic motor and means for automatically shifting the valve to effect a gradual release of exhaust duid.

Figure 1 shows a sectional diagram of a hydraulic control valve and a double piston motor such as used in some machine tool traverse mechanisms.

Figure 2 is similar to Figure 1 except that it shows the various valve members in operative position.

Numeral 10 indicates a valve body similar to that disclosed in Patent No. 2,249,343, granted Iuly 15, 1941. It includes a start and stop valve having ports 16 and 17 separated by a land 18. Fluid under pressure is supplied from a pump 34 through lines 20 Iand 21 to port 16. In the position of valve 15 as shown in Figure l, ports 16 and 17 are cut off rfrom one another. However, movement of said valve to the left will permit the dow of iluid under pressure from port 16 to port 17 and then through line 25, port 26 in the reversing valve and line 27 to the small end 28 of a valve 29. Fluid from port 26 also acts on the left end of by-pass valve 70. Fluid from line also passes through line 35 having a restriction 36 therein to thc right hand end of valve 29 for applying a reduced pressure on the left end of said valve. Between said restriction and said valve, a line 40 having a throttle valve 41 therein provides a restricted exhaust through which fluid is discharged from the right hand end of valve 29. Reversing valve 50 may be actuated to direct lluid under pressure from line alternately through lines 30 and 31 to the head ends of cylinders 60 and 61. Exhaust lluid from said cylinders is directed by valve 50 to exhaust passage 65 which leads to port 66 in valve 29. Said valve in the position shown separates port 66 from port 67 which is connected to exhaust passage 68 leading to the reservoir.

The rod ends of said cylinders are connected by lines 75, 76, and throttle valve 77. Fluid from port 26 acts 2 on the left end of valve 70 to shift said `valve to the right to stop the `free passage of fluid between lines 75 and 76 and direct it through throttle valve ,77.V Lines 78 and 79v .are air-bleeding lines.

Valve 29 is normally held in its lefthand position by constant pressure from pump 84 acting through lines 2t), 35 and restriction 36, The pressure holding valve 29,` to the left is less than pump pressure because of the drop across restriction 36 and because of exhaustline 4Q. This pressure serves to reset valve 29 when start and stop valve 15 is shifted 'to the right, cuttingoif the pressure Ito the left end of valve 2 9. 4 t

When valve 15 is shifted to the left iluid under pressure in port `16 passes through port 17 and line 25 to reversing valve 50 which directsit through lines 30 or.31 to one or the other of cylinders 60 or 61. Exhaust iluid from said cylinders is directed by valve, 50 `to line 65 wh-ich` is blocked by valve 29.

Fluid under pressure in line 25 alsopasses through line 27 tothe left or small end 428, of valve 29 and shifts said d valve to the right at a rate `determined by the setting ot throttle valve 41 in exhaust line 4l). As valve 29 moves to the right it permits a gradually increasing flow of exhaust fluid from `line 65 to pass through port 67 and line` 68 to the reservoir. The gradual unbloeking of exhaust line 65 permits the traverse motor to start smoothly.

We claim:

l. In Ia hydraulic system, a motor, a supply of fluid under pressure therefor, a reversing mechanism for directing fluid to drive said motor alternately in opposite directions, an exhaust passage connected to said reversing mechanism, a ystart and stop .valve for'controlling the supply of iluid to said reversing mechanism, a pressure operated valve` normally blocking the exhaust passage from said reversing mechanismy andemeans` `for shifting said'valve to openfsaid exhaust passageandrneans for controlling the rate of said `shifting movement.

2. In a hydraulic system, a motor, a supply of duid under pressure therefor, a reversing mechanism for directing fluid to drive said motor alternately in opposite directions, an exhaust passage connected to said reversing mechanism, .a start and stop valve for controlling the supply of fluid to said reversing mechanism, a pressure operated valve normally blocking the exhaust passage from said reversing mechanism, connections between said start and stop valve and said exhaust blocking valve operable when said start and stop valve is moved to start position to direct uid to shift said valve to open said exhaust passage and means for resetting said exhaust `blocking valve when said start and stop valve is returned to stop position.

3. In a hydraulic system, a motor, a supply of fluid under pressure therefor, a reversing mechanism for directing iluid to drive said motor Ialternately in opposite directions, pressure and exhaust lines connected to said reversing mechanism, a start and stop valve for controlling the supply of fluid to said reversing mechanism, a valve in said exhaust line for blocking the exhaust passage :from said reversing mechanism, said exhaust line valve having a large area end and a small area end and an intermediate portion, said start and stop valve being operable in the start position to direct fluid under pressure to said small area end, said large area end being under pressure at all times, the supply of uid to said large area end being restricted so that the pressure on said large area end is less than the pressure on the small area end, an exhaust line connected to said large area end and having an adjustable restriction therein, whereby said exhaust valve may be moved by the pressure on the small area end at a rate determined by the restriction in the exhaust passage from the large area end, to gradually connect the axially spa'ced ports to/release said exhaust fluid -from said reversing mechanism.

4. In a hydraulic system, a motor, a supply of fluid under pressurev therefor-a reversing mechanism for directing'uid to drive said motor alternately in opposite directions, a" start and stop valve for controlling the supply of fluid to said reversing mechanism, an exhaust passage connected to said reversing mechanism, -an exhaust valve normally blocking theexhaust passage from saidreversing mechanism, means for directing fluid under pressure to one end of said exhaust valve, an exhaust line from the other end lof said exhaust valve, a restriction in said exhaustline to control the rate of movement of'said Valve when pressure'is applied at the one end thereof, the means fordirecting fluid under pressure to one endk of said exhaust valve including fluid connections between said start and stop'valve and saidexhaust valve for shifting said exhaustv valve in la direction and at a' rate for gradually openingsaid'exhaust passage whereby to cushlion the starting of said motor movement.

5. In a hydraulic system, a motor, a supply of fluid under pressure therefor, a reversing mechanism for directing fluid to drive said lmotor .alternately in opposite directions,y a start and stop valve for controlling the supply of fluid to said reversing mechanism, an exhaust conduit connected to said reversing mechanism, an exhaust valve normally blocking said exhaust conduit, means for directing fluid under pressure to one end of said exhaust valve, a constant supply of uid under pressure to the other end of said valve including a restriction for reducing the pressure on said other end, an exhaust passage between said restriction and said exhaust valve and a throttle valve in said exhaust passage'to control the rate of movement of said exhaust valve when pressure is applied at one end thereof, the means `for directing fluid under pressure to one end of said exhaust valve including fluid connections between said start and stop valve and said exhaust valve for shifting said exhaust valve in a direction and at a rate for gradually opening said exhaust passage whereby to cushion the starting of said motor movement.

6. In a hydraulic system, a reciprocable motor, a supply of' fluid under pressure'for driving saidmotorffevrs'f ing mechanism for directing fluid alternately to opposite sides of said hydraulic motor, pressure and exhaust connections to said reversing mcehanism, means for blocking said exhaust connection and means for shifting said blocking means, and means to control the rate of shifting of said blocking means to release exhaust fluid at a controlled rate until the exhaust line is completely,` opened.

7. In a hydraulic system, a'motor, a supplyof 'uid under pressure therefor, .a reversing mechanism fok? directing fluid to drive said motor alternately in opposite directions, a start and stop valve for controlling the -supply of uid to said reversing mechanism, an exhaust conduit connected to said reversing mechanism, an exhaust valve normally blocking the said exhaust conduit, means for directing uid under pressure to one end of said exhaust valve when said start and stop valve is in start position to open said exhaust valve and for connecting saidend to exhaust when lsaid start and stop valve is in stop position,-

a constant supply of fluid under pressure tothe other end of said exhaust valve for resisting the opening thereof, an exhaust line connected to the same end of said exhaust valve as said constant supply and having ank adjustable restriction therein to control the rate lof opening said exhaust valve, said constant supply of uid under pressure serving to reset said exhaust valve when said start and stop Valve isin stop position.

References Cited inthe le of this patent i UNITED STATES PATENTS 1,748,496 Rownfree Feu'z's, y1930 2,249,343 Balsiger July 15- 1941 2,477,6691 Stephens Aug. 2,l 1949 2,608,824 Kirkham n l' Sept. 2,v 1952 l v FOREIGN iPATENTS l f 373,732

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